1. Field of Invention
The invention relates to an apparatus for intermingling multifilament yarns.
2. Description of Related Art
An apparatus of this kind is known from WO 82/00668, for example. The known apparatus has a thread channel with a generally constant cross-cross-section. In certain cases, the cross-cross-section of the thread channel can vary continuously or stepwise over its length. It can also have constrictions and/or local expansions. The blowing channel of this known apparatus is to have the form of a Laval nozzle.
The intermingling of multifilament yarns is significant because the intermingling promotes the integration of the filaments with one another, resulting in fewer disruptions of thread-guiding elements caused by protruding filaments during subsequent processing of the multifilament yarns. This applies equally for smooth and textured yarns. As a measure for assessing intermingled (or interlaced) yarns, the fixed points per meter of yarn and the mean and maximum opening lengthsxe2x80x94the length between two successive intermingling points, also referred to as intermingling nodesxe2x80x94are determined. During subsequent processing of the yarns, however, stress placed on yarns such as by weaving causes a portion of the intermingling nodes to be removed, so that the mean and maximum opening lengths increase and the fixed points per meter of yarn decrease.
The object of the present invention is to provide an apparatus for intermingling multifilament yarns of the initially cited type that allows multifilament yarns to be intermingled such that the stability of the intermingling properties of these yarns changes as little as possible during subsequent processing.
This object is met by an apparatus for intermingling multifilament yarns, having an intermingling device with a thread channel and at least one blowing channel opening into the thread channel capable of receiving compressed air, wherein the cross-cross-section of each blowing channel increases in the direction of the thread channel and the thread channel for each blowing channel has a first segment before the opening of the blowing channel, a second segment in the area of the opening of the blowing channel, and a third segment after the opening of the blowing channel, whereby the second segment of the thread channel, perpendicular to the axis of the thread channel, has larger cross-cross-sectional areas than those of the first and third segments.
In particular, the width of the second segment increases at least portionwise from the opening of the blowing channel into the thread channel in the direction of a wall of the thread channel opposite the opening.
It has also proven practical for the second segment to have a length that increases at least portionwise from the opening of the blowing channel into the thread channel in the direction of a wall of the thread channel opposite the opening.
Away from the opening of the blowing channel, the expansion of the length and/or width can at first increase and then assume a constant dimension. However, it can also extend over the entire second segment of the thread channel up to the thread-channel wall opposite the blowing channel, whereby it is especially advantageous for the increase in the length and/or width to be continuous.
These measures allow an intermingling assembly to be provided in which the segment of the intermingling assembly in which the blowing channel opens into the thread channel exhibits a significant expansion of the thread channel such that the thread channel in this segment has a significantly larger width than that of the remaining thread channel segments before and after the opening of the blowing channel, and that the thread channel in this segment likewise expands from its base at least portionwise in the direction of the opposite wall of the thread channel. The width of the thread channel is understood to be the cross-cross-sectional dimension perpendicular to the thread channel axis and the blowing channel axis, and the length of the thread channel is understood to be the cross-cross-sectional dimension parallel to the thread channel axis. The base of the thread channel is understood to be the wall of the thread channel running along the side of the thread channel parallel to the thread channel axis, in which wall the opening of the blowing channel is located.
Surprisingly, it has been shown that this approach can, with little energy, produce a high fixed-point density with a high degree of uniformity for the yarns treated with the apparatus of the invention. In many cases, the intermingling can take place at a higher processing speed than when using conventional apparatus for intermingling multifilament yarns. Moreover, the intermingling points exhibit significantly better stability, i.e., the properties allowing assessment of the intermingled yarns undergo significantly less change, even after stressing of these yarns during subsequent processing, than is possible in intermingling using conventional apparatus.